Oudega M, Varon S, Hagg T
Department of Biology, University of California San Diego, La Jolla 92093-0601.
J Comp Neurol. 1994 Sep 1;347(1):115-26. doi: 10.1002/cne.903470109.
The postnatal development of rat corticospinal motor neurons (CSMN) was studied by retrograde tracing with cholera toxin B subunit (CTB) injected into the upper cervical dorsal spinal cord on the first postnatal day (P0), P3, P10, P20, and at adulthood. CTB-labeled neurons were visualized by immunocytochemistry and extensively quantified throughout the cortex. At P0, CSMN were found to an extent similar to that reported in P3 animals with other neuronal tracers, now permitting in vitro studies of neonatal CSMN. Between P0 and P3, the number of labeled neurons increased by 30% to a total maximum of approximately 185,000 in both cortices. The increase occurred throughout the cortex. At P10, the number of labeled CSMN had decreased to 60% of the number at P3. Fewer CSMN were evident particularly in the perirhinal cortex. Between P10 and P20, the number of CSMN decreased further to 52% of the maximal number at P3. This decrease occurred predominantly in the cingulate and parietal cortex. The number of labeled CSMN in rats injected at P0 and analyzed at P20 was 10% lower than the number in P0-injected littermates that were analyzed at P3, which suggests that only a small portion of the "disappearing" CSMN undergoes developmental neuronal death. Thus, the spinal projection of the remaining 38% is apparently eliminated between P3 and P20. Detailed quantitative analysis of the CSMN distribution demonstrated that neuronal death occurs predominantly in the perirhinal cortex. In contrast, axonal elimination of corticospinal projections occurred throughout the CSMN field, i.e., primarily in the frontal, occipital, and perirhinal cortex between P3-P10 and in the cingulate and parietal cortex between P10-P20.
通过在出生后第1天（P0）、P3、P10、P20及成年期将霍乱毒素B亚基（CTB）注入大鼠上颈段脊髓背侧，利用逆行示踪法研究大鼠皮质脊髓运动神经元（CSMN）的产后发育。通过免疫细胞化学法使CTB标记的神经元可视化，并在整个皮质进行广泛定量分析。在P0时，发现CSMN的范围与用其他神经元示踪剂在P3动物中报道的范围相似，现在可以对新生CSMN进行体外研究。在P0和P3之间，标记神经元的数量增加了30%，两侧皮质中标记神经元的总数最多约为185,000个。这种增加发生在整个皮质。在P10时，标记的CSMN数量降至P3时数量的60%。CSMN数量减少，在梨状周围皮质尤为明显。在P10和P20之间，CSMN数量进一步降至P3时最大数量的52%。这种减少主要发生在扣带回和顶叶皮质。在P0注射并在P20分析的大鼠中，标记的CSMN数量比在P3分析的P0注射同窝大鼠中的数量低10%，这表明只有一小部分“消失”的CSMN经历发育性神经元死亡。因此，其余38%的脊髓投射显然在P3和P20之间被消除。对CSMN分布的详细定量分析表明，神经元死亡主要发生在梨状周围皮质。相比之下，皮质脊髓投射的轴突消除发生在整个CSMN区域，即在P3 - P10之间主要发生在额叶、枕叶和梨状周围皮质，在P10 - P20之间主要发生在扣带回和顶叶皮质。
